remark plugin to support frontmatter (yaml, toml, and more)

Usage no npm install needed!

<script type="module">
  import remarkFrontmatter from '';



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remark plugin to support frontmatter (YAML, TOML, and more).


What is this?

This package is a unified (remark) plugin to add support for YAML, TOML, and other frontmatter. You can use this to add support for parsing and serializing this syntax extension.

unified is an AST (abstract syntax tree) based transform project. remark is everything unified that relates to markdown. The layer under remark is called mdast, which is only concerned with syntax trees. Another layer underneath is micromark, which is only concerned with parsing. This package is a small wrapper to integrate all of these.

When should I use this?

Frontmatter is a metadata format in front of content. It’s typically written in YAML and is often used with markdown. This mechanism works well when you want authors, that have some markup experience, to configure where or how the content is displayed or supply metadata about content. Frontmatter does not work everywhere so it makes markdown less portable. A good example use case is markdown being rendered by (static) site generators.


This package is ESM only. In Node.js (12.20+, 14.14+, 16.0+), install with npm:

npm install remark-frontmatter

In Deno with Skypack:

import remarkFrontmatter from ''

In browsers with Skypack:

<script type="module">
  import remarkFrontmatter from ''


Say we have the following file,

title = "New Website"

# Other markdown

And our module, example.js, looks as follows:

import {read} from 'to-vfile'
import {unified} from 'unified'
import remarkParse from 'remark-parse'
import remarkFrontmatter from 'remark-frontmatter'
import remarkStringify from 'remark-stringify'


async function main() {
  const file = await unified()
    .use(remarkFrontmatter, ['yaml', 'toml'])
    .use(() => (tree) => {
    .process(await read(''))


Now, running node example yields:

  type: 'root',
  children: [
    {type: 'toml', value: 'title = "New Website"', position: [Object]},
    {type: 'heading', depth: 1, children: [Array], position: [Object]}
  position: {
    start: {line: 1, column: 1, offset: 0},
    end: {line: 6, column: 1, offset: 48}
title = "New Website"

# Other markdown


This package exports no identifiers. The default export is remarkFrontmatter.

unified().use(remarkFrontmatter[, options])

Configures remark so that it can parse and serialize frontmatter (YAML, TOML, and more). Doesn’t parse the data inside them: create your own plugin to do that.


One preset or Matter, or an array of them, defining all the supported frontmatters (default: 'yaml').


Either 'yaml' or 'toml':

  • 'yaml'Matter defined as {type: 'yaml', marker: '-'}
  • 'toml'Matter defined as {type: 'toml', marker: '+'}

An object with a type and either a marker or a fence:

  • type (string) — Type to tokenize as
  • marker (string or {open: string, close: string}) — Character used to construct fences. By providing an object with open and close different characters can be used for opening and closing fences. For example the character '-' will result in '---' being used as the fence
  • fence (string or {open: string, close: string}) — String used as the complete fence. By providing an object with open and close different values can be used for opening and closing fences. This can be used too if fences contain different characters or lengths other than 3
  • anywhere (boolean, default: false) – if true, matter can be found anywhere in the document. If false (default), only matter at the start of the document is recognized


Example: custom marker

A custom frontmatter with different open and close markers, repeated 3 times, that looks like this:


# hi

…can be supported with:

// …
.use(remarkFrontmatter, {type: 'custom', marker: {open: '<', close: '>'}})
// …

Example: custom fence

A custom frontmatter with custom fences that are not repeated like this:

  "key": "value"

# hi

…can be supported with:

// …
.use(remarkFrontmatter, {type: 'json', fence: {open: '{', close: '}'}})
// …


This plugin applies a micromark extensions to parse the syntax. See its readme for how it works:

The syntax supported depends on the given configuration.

Syntax tree

This plugin applies one mdast utility to build and serialize the AST. See its readme for how it works:

The node types supported in the tree depend on the given configuration.


This package is fully typed with TypeScript. The YAML node type is supported in @types/mdast by default. To add other node types, register them by adding them to FrontmatterContentMap:

import type {Literal} from 'mdast'

interface TOML extends Literal {
  type: 'toml'

declare module 'mdast' {
  interface FrontmatterContentMap {
    // Allow using toml nodes defined by `remark-frontmatter`.
    toml: TOML


Projects maintained by the unified collective are compatible with all maintained versions of Node.js. As of now, that is Node.js 12.20+, 14.14+, and 16.0+. Our projects sometimes work with older versions, but this is not guaranteed.

This plugin works with unified 6+ and remark 13+.


Use of remark-frontmatter does not involve rehype (hast) or user content so there are no openings for cross-site scripting (XSS) attacks.



See in remarkjs/.github for ways to get started. See for ways to get help.

This project has a code of conduct. By interacting with this repository, organization, or community you agree to abide by its terms.


MIT © Titus Wormer